The present invention relates to a catalytic composition comprising titanium and phosphorus, its preparation and its use notably as an esterification catalyst of at least one epoxide by at least one carboxylic acid anhydride.
The present invention particularly relates to the production of esters from at least one epoxide and at least one carboxylic acid anhydride, for example a monocarboxylic acid anhydride.
It also relates to the production of a condensation copolymer or polyester with a regular alternation of each type of compounds reacted and resulting from the condensation of at least one epoxide on at least one cyclic anhydride of a dicarboxylic acid.
This type of esterification or polyesterification is different from the conventional process which employs a dihydroxyl compound (or diol) and an anhydride or a carboxylic acid, notably in that the reaction involves the opening of the oxirane ring and in that no volatile matter is generated during the reaction. It is also different in that the reaction temperature does usually not exceed 150.degree. to 200.degree. C.
Numerous works have been published on the synthesis of esters and more particularly of polyesters from epoxides and anhydrides of carboxylic acids in the presence of catalysts of different types. These works show that one major problem encountered during the reaction of the epoxide on the anhydride in order to obtain an ester or a polyester is linked with the homopolymerization of epoxide.
In the case of the condensation between an epoxide (or epoxide derivative) and a cyclic anhydride of a dicarboxylic acid, these works are for example summarized by LUSTON and VASS (Advances in Polymer Sciences 1984, Vol. 56, p.91 and following pages) or by ISHII and SAKAI (Ring opening polymerisation, p.13 and following pages, published by K. C. FRISCH and S. L. REEGEN, MARCEL DEKKER 1969).
In the case of the reaction of an epoxide on a dicarboxylic acid anhydride in order to produce an alternate polyester, the homopolymerization of the epoxide leads to the obtaining of a sequenced polyether-polyester or to mixtures of polymers, in particular when LEWIS acids (TiCl.sub.4, BF.sub.3, are used as condensation catalysts. In order to overcome this drawback, it has been suggested, in prior art, to utilize anionic or coordination catalysts.
FISCHER (Journal of Polymer Science 1960, Vol. 44, p.155 and following pages) has shown that the use of a tertiary amine as the condensation catalyst of an anhydride on an epoxide allows obtained an alternate condensation. Still, this type of catalyst is ineffective in the case of maleic anhydride, probably because of the complex side reactions with the amines at the level of the double maleic bond. Other types of anionic catalysts such as the salts of alkaline metals or the tetra-alkylammonium salts have also been utilized.
For example, WADILL, MILLIGAN and PEPELL (Industrial and Engineering Chemistry, Product Research and Development 1964, Vol.3 Part 1, p.53 and following pages) describe the use of lithium chloride in the presence of protonic substances at 150.degree. C. These authors suggest that the homopolymerization of epoxide represents part of their process. As an example of coordination catalysts, the dialkylzinc mentioned by INOUE et al. (Makromoleculare Chemie 1969, Vol.126, p.250 and following pages) can be cited; in fact, this type of coordination catalyst is only applicable, according to INOUE et al., to phthalic anhydride.
Other catalysts, based on transition metals, have also been described before. FISCHER (cited above) thus observes a partial homopolymerization of glycidic epoxide during its polycondensation with phthalic anhydride in the presence of tetrabutyl titanate.
U.S. Pat. No. 3,546,176 describes the use of tetrabutyl anhydride for producing unsaturated polyesters from anhydrides of unsaturated acids and epoxides. Nevertheless, as confirmed by a test performed by the applicant and described hereafter, this catalyst does not allow obtaining, with a sufficient reaction velocity (a velocity which requires a relatively high temperature), a polymer with a good alternation of the units stemming from the anhydride and the epoxide.